i've got thanks and btw how i go about solving the following:
Write the main() method to call getNum () in order to get a series of positive integers between 1 and 9999. It will stop calling when the user enters 9999. The program will compute and display the following:
a) product of all the numbers,
b) average of all the numbers,
c) difference between the biggest and the smallest number

You've got the code for reading in number from a user. Now you need to add some logic to the loop where you read these numbers to do the computations as per the program requirements.
Start with a program with a loop that prompts for the next number and exits the loop when the number is the end number value.
When that works, move to the next part of the problem.